The Time Triggered Protocol (TTP) is an efficient real-time protocol for automotive networks. The TTP class C version of the protocol provides all services needed for the implementation of safety critical distributed fault-tolerant class C systems. The TTP class B version of the protocol provides an economical solution to class A and B applications. Both protocol versions use the same frame format on the communication network and the same application software interface. This paper describes the protocol objectives, compares the functionality of TTP/C and TTP/B, and focuses on the fault management strategy of the TTP/C protocol.